Cost

• Since hot steam humidifiers have a heating element that cool mist vaporizers do not, hot steam humidifiers cost more money up front. They may also cost more over the long term, as they require more electricity to run.
  
  

Safety

• Cool mist vaporizers are recommended by pediatricians because they do not pose the burn risk to infants or toddlers that hot steam humidifiers do.
  
  

Bacteria Growth

• Cool mist vaporizers are more likely to promote bacteria growth sooner than their hot steam counterparts. However, both types of machines require regular cleaning to inhibit the growth of bacteria. The Mayo Clinic recommends using a bleach-water combination to effectively clean the water tank and basin.
  
  

Mineral Dispersement

• Cool mist vaporizers are more likely to disperse minerals from hard water into the air, so using distilled water is recommended. Hot steam humidifiers, on the other hand, are unlikely to disperse minerals, so tap water is a viable option.
  
  

Noise

• Hot steam humidifiers tend to be quieter than cool mist vaporizers. Some cool mist vaporizers, however, are equipped with a silent feature.